The beneficiation of ore, particularly iron ore, conventionally has involved the use of various combinations of process setps such as crushing, grinding or milling, concentration or separation by size or weight such as by a screen and/or specific gravity, as by a hydraulic classifier, and concentration with the aid of flotation agents, as in froth flotation, or by means of a magnetic classifier. See, for example, Lawver, U.S. Pat. Nos. 3,337,328, Braund, 2,468,586, Keck, 2,428,228, Hubler, 2,352,324, Ferris, 2,336,854, Rakowsky et al, 2,325,149, Wade, U.S. Pat. No. Re. 22,191, Weed, U.S. Pat. Nos. 2,014,405 and DeVaney, 2,388,471.
For purposes of reviewing my disclosure the reader may be interested in the details of the last mentioned patent to DeVaney, wherein it may be seen that the ore is ground and crushed, sized by a classifier in a closed loop, and concentrated in a magnetic separator, the concentrate therefrom being further concentrated in a flotation circuit where the high iron content "underflow" is retained as product and the "siliceous froth", still containing significant amounts of iron, is recycled to a ball mill (which must be set at a finer grind than the original grinder) through another closed loop classifier, and then to a magnetic separator.